This invention relates to electro-optic transducers and optical transmission devices, and particularly to light-emitting and detecting transducers and light transmission systems therefor, and to devices and methods for aligning such systems and transducers. This invention also relates to fiber-optic cable, and particularly to termini, connectors, alignment devices and optical systems and methods for terminating and connecting fiber-optic cable.
The provision of optical transmission systems in the use of electro-optical transducers long has presented problems, particularly in communications systems using fiber-optic cable for transmission.
Coupling to electro-optical transducers has been complicated by the very small diameter of light beams transmitted as well as the small size of semiconductor devices often used to generate or detect the signals. Any foreign objects, such as dirt and dust, which accumulate in the optical path of the signals can seriously compromise the integrity and operability of the system.
Difficult problems specific to the use of fiber-optic cable for transmission also are well known. For example, providing suitable end termini and connectors for connecting two fiber-optic cables together long has been a demanding problem. The problem has been exacerbated by the prevalent use of single-mode fiber-optic light conductors of an extremely small diameter, such as 8 micrometers (0.008 millimeters). Aligning the cables accurately usually is a time-consuming and exacting process.
Standard commercial butt-joint type single-mode fiber-optic connectors suffer from numerous problems. First, they are relatively delicate, sensitive to dirt, difficult to clean, and easily damaged. The problems are even greater with multi-channel connectors which must function in a hostile environment.
In the past, various proposals have been made to improve such prior connectors. Included are proposals to use expanded-beam type connectors. Such connectors use different types of lenses to collimate and spread the beam of light emitted from the optical conductor. Then, an identical lens system is used to terminate another cable end to be coupled to the first cable, and the two termini are connected together. The second lens system re-focuses the beam on the second optical conductor so as to transmit the signal through the second cable.
The optical systems used in such prior expanded-beam connectors include spherical lenses, “GRIN” lenses (graded index lenses) and molded aspheric lenses to expand and collimate the light beam.
The advantages of such expanded beam connectors includes minimizing the sensitivity to dirt and lateral misalignment and to the size of the gap between the ends of the optical conductors.
However, prior expanded beam connectors and techniques suffer from several problems. Such problems include relatively high optical losses and high cost. In fact, the cost has been considered to be prohibitive for many commercial applications. Furthermore, it is believed that the prior designs are relatively difficult or even impossible to be installed correctly in the field; that is, outside of a factory, laboratory, or other such facility.
Accordingly, it is an object of the present invention to provide an electro-optic transducer device, and a fiber-optic cable terminus, connector and alignment device and method which overcome or alleviate the foregoing problems.
More specifically, it is an object of the invention to provide an expanded-beam type terminus and connector and alignment device and method which overcome or reduce the problems experienced with prior expanded beam devices.
In particular, it is an object of the invention to provide an electro -optical transducer and fiber-optic cable terminus and connector which has as many of the following favorable attributes as possible: low cost; low loss; low back-reflection; small size; ruggedness; insensitivity to dirt; ease of cleaning; capability of being installed in the field; high optical power throughput capability; suitability for use in hostile environments; and capability of being standardized.
It is also an object of the invention to provide such a device and method capable of operating with single mode optical conductors; with multi-channel cable; is relatively non-dichroic; and preserves polarization of the light being conducted.
It is another object of the invention to provide an integrated multiple-reflector optical device for expanding and collimating light beams and particularly fiber-optic cable light beams.